1. Field of the Invention
The invention relates in general to a power calibration system, and more particularly to a high precision, low cost power calibration system.
2. Description of the Related Art
As requirements for high volume storage mediums become greater, compact disks (CD) play a more important role. During the manufacturing process pits are created on the CD by the optical pickup unit (OPU) of the CD recorder when it emits a light beam on the dye layer; however, lands are formed on the CD when no light beam is emitted thereon. The pit has a lower reflectivity than the land and the pit and the land represent the information of 0 and 1 respectively.
However, pits produced by laser beams of different output power levels from different CD recorders are usually shaped differently, which will cause difficulty in the process of reading information. This is a result of the variation in the assembly of the OPU and inconsistencies in the photo diode properties. Therefore, the CD recorder has to have its laser power calibrated prior to the fab-out stage so that the OPU can provide laser beams of the correct power.
Traditionally, laser power is measured by a power meter and a sensor probe, which together cost about more than one thousands of US dollars. If each service center around the world must be equipped with such an apparatus, it increases manufacturing costs a great deal.